Sunday, June 26, 2011

By moving forward on their mission to convert the U.S. fleet of Space Shuttles into museum pieces, the administration has shifted NASA into neutral. America’s multi-billion dollar investment in the International Space Station (ISS) and our access to space is in jeopardy. As a result of the termination of the Shuttle program, we have no means to assure ISS health and safety or the continuation of manned-space for the coming decade.

True, the “retirement” of the Shuttle is an event long-planned — announced in 2004 as part of the Vision for Space Exploration (VSE). But contrary to common belief, the VSE plan to retire Shuttle was not because it is “too dangerous to fly” or “outdated technology.” Rather, its retirement was intended to free up that portion of the NASA budget it consumes, with that money going to the development of new space vehicles for human missions beyond low Earth orbit—the limit of Shuttle’s reach. In 2004, it was understood that the old and new systems would not seamlessly overlap in time, but in the past eight years, the “gap” of time between the last flight of the Shuttle and the first flight of whatever system succeeds it has increased alarmingly from months to years and now finally, to infinity. The spaceflight “gap,” once seen as risky, now looms before us a black hole of uncertainty.

Our country is set to eliminate the one proven system remaining under our control that can access both space and the ISS. The only thing clear about the administration’s current plan is the confusion surrounding it. Initially, the proposal was to replace a government-built and operated space transportation system with a contractor-controlled one. Coined “New Space,” these contractors were to provide access to orbit for both cargo and people. The New Space path was already being pursued under VSE – not as an immediate replacement for a government system but as an interim adjunct to it. The belief and hope of the agency under VSE was that a transition period would allow commercial companies to design, build and perfect their systems into operational status, while working through anticipated difficulties in technology, budget and program set-backs. As NASA began transitioning away from ISS re-supply, workforce continuity would remain as we began building systems for missions beyond low Earth orbit.

New Space advocates claim that as “commercial” entities, they can provide the needed capabilities to service ISS faster and at a fraction of the cost of either Shuttle or a new government system. If this promise sounds familiar, it is because thirty years ago, as part of the marketing for Shuttle, we heard similar arguments. What we learned then was that spaceflight is difficult, unforgiving and expensive. While one could argue that Shuttle is an inherently flawed transportation system, it still is a working system and it works because we expended the time, experience and money needed to make it work.

Any of the new systems (“commercial” or government) will not have the unique capabilities of Shuttle. Unlike the current “capsule” configuration of the new planned spacecraft, Shuttle carries crew (7 people) and cargo, the latter in enormous quantity – over 24,000 kg per flight. The Russian Soyuz crew (3 people) or Progress cargo vehicles (2350 kg) deliver but a fraction of this so-called “up mass” (the amount of material delivered to the ISS) per launch. The large payload capacity of Shuttle was necessary to build the ISS. Now that Station is complete, one might argue that smaller amounts of cargo delivery are adequate to maintain it. This might be true for normal operations but what happens if a catastrophic failure occurs? The largest part that can be sent to Station will be less than ¼ the mass that Shuttle can deliver. An example of a possible critical need would be a de-orbit motor. If the ISS became uninhabitable or suffered a failure, its orbit would begin to decay. In order to keep over one million pounds of debris from re-entering Earth’s atmosphere, breaking up and falling onto that part of the globe where 98% of humanity resides, a rocket engine must be delivered and attached to send the ISS on a controlled descent into uninhabited areas over the oceans.

Beyond the safety issue surrounding the loss of Shuttle’s capability to deliver to LEO, Shuttle is also an operational service platform when on-orbit. It has an airlock, permitting crew to conduct EVA to repair and maintain ISS and other spacecraft on a routine basis. The only way crew can EVA from the Shuttle’s successor will be to depressurize the entire vehicle, a complex and dangerous maneuver that will likely be conducted only in the event of an emergency. The large stable base of the Shuttle (100 tons on-orbit) permits it to have a robotic operating arm to use both in conjunction with space-walking astronauts and independently. Balky space satellites and parts are firmly held in its cargo bay while repairs are safely completed. Astronauts attempting to service small-mass, free flying satellites find that they drift away, rotating at the slightest touch. The Shuttle serves as a “hangar” in space in which repairs and maintenance can be safely and efficiently accomplished.

Ignoring these considerations is troubling, but might be less so if there were any evidence that serious thought had been given to them. Under our previous direction, it was fully understood that a Shuttle replacement system would be in the pipeline and by now (a bit late and after the usual developmental problems) would have been cutting metal. In contrast, we now have nothing but policy chaos. Summary cancellation of the Constellation rocket system may have been justified on grounds of cost, but the wishful thinking represented by its imaginary replacement is simply unconscionable. Despite the loud and persistent claims of many in the space media, “commercial” providers are not going to produce anywhere near the same capability that Shuttle gives us, even if, through some miracle, they are successful in both budget and schedule. Yet, in the coming decade, essentially the same amount of spending is proposed.

New Space, for all its marketing and eager supporters, has entered a realm where their success on the time frame and budget envisioned – that will greatly affect us all—is uncertain. For a country in troubled times, it is foolhardy, short-sighted and financially ignorant to destroy the one working space access system we have. For New Space cheerleaders to herald the new path as a wonderful anomaly in a sea of otherwise benighted government meddling is to be blind to the reality of the current climate and of the importance of the job they have been handed. The “New Space” companies that NASA currently funds will have the same problems of money, time and architecture that space projects traditionally have had. How long will our rapidly growing government (with its rapidly shrinking discretionary budget) patiently support “commercial” New Space efforts?

In the past, we were assured of government’s ability to project power and protect national interests in space. After the last Shuttle flies, NASA will idle in neutral for the indefinite future. Our space program is adrift—a barometer of our national condition. Sometimes events dictate a course correction. Now is not the time to stop flying Shuttle.

An impact melt pool (lower right) within Das crater. Nearby boulders are the result of fractured impact melt which have migrated downslope and formed talus (upper left). Uphill direction is to the top left. LROC Narrow Angle Camera (NAC) observation M136091866, LRO orbit 5189, August 10, 2010; field of view is 240 meters. See the 600 meter-wide, full resolution LROC Featured Image HERE [NASA/GSFC/Arizona State University].

Drew EnnsLROC News System

Das crater (35 km diameter) is located just northeast of the South Pole-Aitken Basin. The portion of the floor in the opening image is a smooth and flat pool of impact melt. A large amount of energy is created and absorbed by both the bolide and the target during an impact event. The bolide is very nearly vaporized, and a large portion of the target is melted, fractured, and redeposited elsewhere as ejecta. Impact melt, unlike most ejecta, stays primarily within its parent crater, forming intricate patterns as the melt flows downslope and gathers in large pools. Occasionally, impact melt will also spill out of the crater, forming exterior melt deposits.

Context images of Das crater (26.6°S, 223.2°E). On the high northeast rim of 4 billion-year old South Pole Aitken basin, 280 km northeast of some of the deepest excavations within the Apollo impact basin just inside SPA [NASA/GSFC/Arizona State University].

But how do scientists know that this pond within Das crater is in fact impact melt? Solving this puzzle requires the geologic context of this small pond within the crater. As discussed in yesterday's Featured Image, the volume and texture of the pond help piece together the puzzle. Das' crater floor in the context image is not smooth or flat and is made up of several pools of ponded material. This is unlike Jenner's singular flat crater floor. The distribution of these ponded materials gives us our next clue! The ponds are at separate elevations within the crater and flow downslope! This is not what we expect to see in a mare flooded crater when a massive amount of lava is sourced from a low elevation. These observations all point to impact melt as the best explanation for this pooled material.

There is a good piece in today’s Telegraph UK by David Robson of a fateful one-hundredth anniversary – the Midwinter Dinner — June 22, 1911 held in Robert Falcon Scott’s Ross Island hut. A year earlier, Scott and the crew of the Terra Nova had set off for the Antarctic and the south pole. It was a carefully planned and perilously financed expedition, a classic journey of the “golden age” of polar exploration. At the time, Scott had no idea that Roald Amundsen, the famous Norwegian polar explorer, had turned his north pole-bound Fram due south and unknown to Scott and his men, was at that moment camped on the opposite side of the Ross Sea, carefully planning a summer dash to the south pole.

Of what relevance is this story to space and the Moon? To me, it encompasses and restates several themes I have developed on this blog about the nature of exploration and sustainable presence in a hostile environment. The theme of the Telegraph article is that Scott’s expedition was all about science. His team included geographers, geologists, biologists and meteorologists. They collected specimens, documented phenomena, made observations, and conducted experiments. Scott’s expedition was organized like a carefully planned military campaign. Although conducted under the command structure of the Royal Navy, it was a civilian expedition, funded by subscription. No tax money was used and financing was always a major headache for Scott.

A theme running through Robson’s article has been a recurring motif in polar literature for many years – that while Scott and his team were honorable scientists, conducting true “exploration,” Amundsen and his men were publicity-seeking interlopers, cads and bounders who treacherously misled the noble and long-suffering Scott about their true intentions, and who then had the cheek to actually race ahead to beat Scott to the south pole. This theme has long been a part of British polar exploration literature – the sting of Amundsen’s victory in the race to the south pole still hurts. A book and television series on the polar race published over 20 years ago attempted to deconstruct this myth and was roundly blasted in the British press at the time.

But the Telegraph piece contains a fundamental contradiction. It takes great pains to show Scott’s expedition as a scientific, scholar’s investigation, as opposed to the “PR stunt” of Amundsen’s polar dash. If this is true, then of what importance was priority in attainment of the south pole anyway? The pole is merely one more data point on a string of measurement stations. Scott’s purpose was science, not stunts. He led a carefully planned and documented expedition to unravel the secrets of the Antarctic. By arriving at the pole after Amundsen, what could it matter? He still had his fossils, rock samples and observations, did he not?

Obviously there was much more at stake than admitted, both then and now. The great age of polar exploration was not about science, any more than Apollo to the Moon was about our first visit to another world. Large public spectacles like polar exploration were both theater and geopolitical struggles. In the decades leading to the Scott and Amundsen efforts, many had tried (and failed) to take the north pole. An entire subculture of polar explorers had developed, each group knowing of the other groups’ efforts in the desperate competition to be the first to stand on top of the world. Establishing priority became an obsession with many and proof was difficult to obtain (the Frederick Cook-Robert Peary controversy over who was the first at the north pole continues to this day).

Both Scott and Amundsen lived in this milieu. But they were also Edwardian gentlemen and sporting conduct was natural and expected behavior. Amundsen’s “sin” was that he discarded the fig leaf of “science” and exposed to public view the raw power politics involved in exploration. In the words of the President of the Royal Geographic Society Leonard Darwin (son of Charles), Amundsen had not “played the game.”

The idea that exploration is for scientific purposes stems largely from this golden age of polar exploration. In part, the conflation developed because of the need for Britain to attribute a noble and uplifting rationale to Scott’s polar trip. His tragic death on the way back from the south pole was made especially bitter by the loss of priority – when Scott arrived at the pole, he found that Amundsen had beaten him there. One way to make this unpleasant pill more palatable was to assign noble motives to Scott and base ones to Amundsen. Hence, a mythos developed, sanctifying Scott as a martyr for science and depicting Amundsen as a crass interloper. An unnoticed side-effect of this storyline was the simultaneous sanctification of science as the rationale for exploration. This attitude is typified by a comment from an astronomer in the early days of implementation of the Vision for Space Exploration in 2004 that “exploration without science is tourism.” Scott’s hagiographer could not have put it better.

But this concept, developed one hundred years ago to salve the outrage and hurt feelings of a disappointed nation, does not serve us well as we contemplate the exploration of our Solar System. Exploration traditionally has a much broader meaning. Columbus, Balboa and Magellan did not undertake their expeditions for science. They sought wealth and power; they envisioned new lands for settlement and the spread of their own culture. In short, the view of “exploration” prior to being redefined during the golden age of polar exploration had little to do with science and much to do with wealth creation, power projection and settlement.

Science is great and knowledge always has both practical and intangible value, but it is a small part of the motivation for exploration. The Antarctic is a continent for science but only by mutual agreement of the international community. The riches of Antarctica remained locked up as scientists hunt its surface for fallen asteroids and evidence for global warming. Some think this is a template for space exploration; others find such an idea anathema. Science stagnates when exploration stalls. If we were exploring the Moon, scientists would find a bounty of extraterrestrial samples and have an unparalleled opportunity to study the record of Earth’s climate locked in eons of undisturbed solar wind in the lunar regolith. Once humanity and technology are able to utilize the Moon’s resources to break the tyranny of the rocket equation, the vast riches of our Solar System will open to explorers, entrepreneurs, settlers, and scientists alike.

We explore for many reasons. There are many valid and important national interests of which science is but one. Scott understood this; hence, his disappointment at his own failure to reach the pole first. As we prepare to leave the Earth on a more permanent basis, it is well to look back at this curious and (I would say) singular interval in history – a time (so we are told) when science became the rationale for exploration. It wasn’t true then and isn’t true now.

Related side-note: Videos of my Space Pioneer Award talk at the recent 2011 International Space Development Conference in Hunstville AL have been posted in two parts, HERE and HERE. This talk touches on several of the themes I mention above. The slides from my talk are available for download HERE.

This small ridge is a one of several wrinkle ridges within Jenner crater.

Wrinkle ridges often form in mare units due to compressional stress. The floor of Jenner crater was completely covered by lava, and the weight of the lava may have resulted in a slight sinking of the crater floor, resulting in compression and buckling of the mare deposit. The mare was thick enough that only its central peak and a few terraces remain unburied! But how are scientists sure that this crater is filled with lava and not impact melt?

Context image of Jenner crater. The field of view of the LROC Featured Image close-up, released June 21, 2011, is located in the white box. LROC Wide Angle Camera (WAC) contextual field of view above is 100 km. View the full-size WAC image HERE [NASA/GSFC/Arizona State University].

Our first clue are the wrinkle ridges that commonly form in mare, but this is not enough evidence. Other useful observations are the volume and texture of the crater floor. Tycho crater (86 km diameter) is an example of a crater with impact melt covering most of its floor. However, Tycho's floor has a rougher, more chaotic texture than Jenner.

Jenner's floor is smooth, much more similar to a mare surface than to the impact melt deposits within Tycho. The smoking gun comes from mineralogical data. Clementine multispectral data of Jenner shows a mafic signature, indicative of a mare unit. Looking at these variables, Jenner is more similar to other mare flooded craters, such as Archimedes crater, than to Tycho crater.

Just beyond the 90th Meridian east, Jenner (at upper center) is a challenge for Earth-bound observers, who's seeing is limited to a grand total of only fifty-nine percent of the Moon's surface, and then only during the most favorable of conditions, like the lower elevation ponds of Mare Australe that surround it. In the LROC WAC mosaic of the Moon's eastern hemisphere, released late last year, it's an easy find in south-southeast [NASA/GSFC/Arizona State University].

The interior floor of Tycho is covered by blocks, boulders and impact melt textures. The impact melt deposits often show networks of fractures visible at the LROC Wide Angle Camera pixel scale of 100 meters.

At Narrow Angle Camera resolution with very illumination incidence angles (illuminated almost along the horizon), the extremely complicated and chaotic nature of the surface is striking.

Simulated view of Tycho's chaotic interior floor from high upon the craters sharp central peaks looking toward the southwestern rim beyond, from a still lifted from the magnificent Kaguya Terrain Camera panorama video, offering an breathtaking tour of Tycho's anatomy, released May 27, 2009 [JAXA/SELENE].

Impact melts have extremely complicated thermal histories. When the impacting meteoroid's kinetic energy is large enough, the initial temperature of an impact melt can be much higher than that of normal magma, which is driven by volcanic activity. The melts are mixed together with ejecta debris, flow down slopes and puddle; loosing heat and increasing in viscosity with time. Once settled in the crater floor, solidification starts at the top and the bottom (chilled margins), and continues little by little to the melt volume interior. Any kind of deformation during this time (for example, the isostatic rebound of the crater floor, uneven thermal contraction, or late flows pushing pre-existing melts) will disturb the solidifying melt surfaces to make the chaotic patterns and sometimes cause local "eruptions" of melt onto the newly solid layer.

Yuri Goryachko and friends at Astronominsk are among the premier lunar (and planetary) photographers on Earth. The image above, from a mosaic captured April 6, 2009, offers an enhanced color view of Tycho, the crater who's wide-ranging ray system dominates the Moon's southern hemisphere and beyond as seen with the naked eye. Tycho is not an unusual crater by any standard. It's rays and rough hewn appearance are indicative of its relative youth, only 109 million years old - and not yet "optically darkened" by the relentless bombardment of meteors, micrometerors and hard radiation that gardens and changes the composition of the Moon's immediate surface (and albedo) every 2 million years or so [ASTONOMINSK].

Not all "permanently shadowed regions," or "PDR's," on the Moon are created equal. Not long prior to the LCROSS impact (near the center of the permanently shadowed interior of Cabeus crater, in the LROC Wide Angle Camera (WAC) monochrome mosaic seen above) this nearside crater was discovered to be perhaps the "juiciest" spot on the Moon. At the same time craters further south, closer to the Moon's south pole (and presumably more completely and "permanently shadowed," were dryer. Some of these regions, deep and adjacent to one another showed very different "volatile profiles." And just as Lunar Pioneer seemed to show with far less resolution of data, late in the last century, "volatiles" like water molecules show a profile in wider areas that are not permanently shadowed. Repeated orbital passes by LRO's laser altimeter (LOLA) have now brought this shadowed area to light in detail [NASA/GSFC/Arizona State University].

Goddard Space Flight Center, June 15 - On October 9, 2009, the Lunar Crater Observing and Sensing Satellite (LCROSS) impacted a permanently shadowed region in Cabeus Crater near the Moon's South Pole. Since then, data from LRO and LCROSS have revealed the presence of volatiles, including water, in Cabeus. This LOLA image shows details of the region within Cabeus that cannot be seen in visible imagery (due to the aforementioned permanent shadow). LRO's polar orbit allows for a high density of measurements near the Moon's poles, which in turn gives us high-resolution data of the lunar polar topography.

Thursday, June 16, 2011

Remembering where we parked. - Together with Charlie Duke, John Young (who later piloted the first Space Shuttle flight) brought the Apollo 16 lunar module down on the plain northwest of the Descartes Formation "a little long," or west of the center of the mission's landing ellipse. The LM Descent Stage exhaust blew the relatively darkened, optically mature immediate surface dust away, exposing a halo of slightly lighter material. Their foot and rover wheel trails left behind during their 1972 expedition, nearer the lander, in turn churned darker materials back into the sunlight, making their distinct sign clearly visible nearly 45 kilometers overhead in this image captured by the LROC Narrow Angle Camera last November [NASA/GSFC/Arizona State University].

Tycho is a young and prominent rayed crater on the lunar nearside. During the impact that formed Tycho crater a large mass of impact melt was thrown out on its north side that resulted in a series of beautiful flow patterns. The melt ponded in several topographic lows, and as they cooled their upper crusts fractured, often in polygonal patterns.

Today's Featured Image shows a set of crisply preserved polygonal fractures. Small chains of pit chains are also seen in conjunction with the fractures. Are these pits nascent fractures that never fully developed? Or perhaps partially collapsed tubes that melt flowed through? If the latter, might there be open passages that astronauts could venture into and explore?

In January 1968, Surveyor VII (arrow) landed only a kilometer from the impact melt pond immediately to its northeast, caught once again by LROC's NAC, almost exactly forty-three years later. The plucky vehicle's distinctive square solar panel and profile can easily be seen in its long shadow (see full-resolution crop below) near the center of the full LROC NAC frame from which the LROC Featured Image above was snipped [NASA?GSFC/Arizona State University].

Surveyor VII - A very successful lander, the last U.S. unmanned lunar lander and last of an outstanding program is caught standing sentinel awaiting a valuable examination of the effects of nearly 575 two-week long blistering hot lunar days and an equal number of two-week long numbingly cold lunar nights [NASA/GSFC/Arizona State University].

Explore the polygonal fractures (and find Surveyor 7) north of Tycho by viewing the full NAC image!

The J-2X, designed and built for NASA by Prat & Whitney Rocketdyne, is the new generation design for the engine that powered Apollo-Saturn V's Third Stage through Trans-Lunar Injection from 1968-1972. The complete redesign is ready for live-fire testing. Above a Shuttle main engine undergoes testing at Stennis Space Center two years ago [NASA/Stennis].

al.com

Bay St. Louis. Mississippi- NASA's new J-2X rocket engine is ready for its initial round of testing after being installed Saturday in the A-2 Test Stand at the space agency's Stennis Space Center in Mississippi.

The fully assembled engine will undergo a series of 10 test firings starting this month that will last several months.

"An upper stage engine is essential to making space exploration outside low-Earth orbit a reality," Mike Kynard, manager of the J-2X upper stage engine project at NASA's Marshall Space Flight Center in Huntsville, Alabama, said in a news release. "The J-2X goes beyond the limits of its historic predecessor and achieves higher thrust, performance, and reliability than the J2. We are thrilled to have the engine in the test stand to validate our assumptions about engine performance and reliability."

This observation naturally went over well with the crowd at the ISDC and the subsequent posting of a video of Jeff’s talk sent many space cadets of the internet into spasms of joy that someone would finally state in public the True Belief – humanity’s destiny is among the stars. Finally, out of all the confusion and bickering about heavy lift launch vehicles, depots, destinations, and crew vehicles, we have at last a clear articulation of the direction and purpose for the human space program.

There’s only one problem: it’s not the right goal for NASA.

First, let there be no misunderstanding. I agree that settlement and the expansion of humanity into space is indeed a noble and desirable thing — I call it the “ultimate rationale” for human spaceflight. By that, I mean that the idea of people going into space to live there, wherever our desires and aspirations may lead, is an objective of our species, a desire to spread human culture beyond its planetary cradle into the cosmos. That’s a different concept than making space settlement the objective of NASA’s human spaceflight program. I do not think such is an appropriate goal for a federal program that competes with all the other projects in the discretionary budget.

To most outside space circles (as well as to a surprisingly sizable number within the space community), space is a hostile, barren wilderness, with no harbor for man and his works. Their solution is to build machines that can be sent to return information from which we will decipher the secrets of the universe. Moreover, these people can think of at least two dozen different things they would rather spend that money on; you can bet that dreams of space settlement would fare poorly in comparison.

Another problem with “settlement” as an objective is that the metrics for success are difficult to define. When is space “settled” – when a single human lives permanently off planet? When a community is thriving on another world? How large a community and where? Buying into settlement as our goal means making a permanently moving target your objective; no matter what milestone is reached, you’ve never actually achieved your “goal” of settlement (for a current implementation of this mentality, see “Search for Extraterrestrial Life”).

Finally, settlement is a poor goal for a federal space program because it is so distant. No one seriously believes that humans will live in space or on another world permanently within the next several decades. Government programs can barely tolerate time horizons beyond one presidential term, let alone a multi-decadal trek through near-space. True enough, we can devise a program that delivers significant milestones toward the goal of space settlement within such time frames, but with such a nebulous end point receding into the distant future, it will lose its luster and consequent political support very quickly.

In contrast to Greason’s proposed “settlement strategy,” I have tried to frame a slightly different path for our national space program. Our “goal” is to expand human reach beyond LEO, first into cislunar space and then into interplanetary space (by “reach,” I mean the routine access of people and machines to any point in space where we need or want these capabilities to do whatever job we need to.) The “strategy” to accomplish this extension is to establish a resource-processing base on the Moon to make fuel for a cislunar space transportation system. A “tactical” implementation of this strategy is a robotic ISRU architecture, which will create our first foothold on another world.

What is the advantage of this path over Greason’s settlement sequence? For one thing, we can accomplish it much sooner than human settlement of space will ever occur; an operational lunar resource processing base can be up and running within 10-20 years of program initiation. Second, a space faring transportation system is relevant to critical national needs, specifically, our ability to maintain and extend the constellation of economic, scientific, and national strategic satellite assets that reside in cislunar space. By adopting this goal, we start from a position of political strength: we don’t have to convince Congress about our destiny among the stars, we just have to point out the critical dependence of modern technological civilization on our satellite assets in the volume of space between LEO and the Moon. Right now, those satellites are all designed as one-offs: build, launch, use, and discard. We want to change that template to build, extend, maintain and expand. Developing lunar resources to fuel a space transportation system allows us to do this and more.

By doing these things we lay the groundwork for space settlement. All agree that settlement requires the ability to access and use local planetary resources. Going to the Moon to harvest its polar water begins that process. If you want to look upon this as the first step in the settlement of the Solar System, be my guest. But I suggest that making lunar return relevant to important national economic and security objectives is more likely to help consolidate political support than setting the goal of “settlement” as NASA’s objective. NASA’s founding charter, the Space Act of 1958, lays out many different objectives and goals for the agency; space settlement is not one of them. But routine access to cislunar space is; cislunar space is specifically mentioned in the new NASA Authorization Act of 2010.

Settlement is a valid long-term goal for humanity in space – but we must have something with a practical and political payoff in the near-term.

Saturday, June 11, 2011

Detail from the Digital Elevation Model (DEM) of Sinus Iridum, an area of high interest to the Chinese Lunar Exploration Program surveyed by the PRC's second lunar orbiter Chang'e 2, which has now left the Moon's vicinity and departed for "Outer Space" [CNSA/CLEP].

Deng Shashaxinhua

Beijing -- China's second moon orbiter Chang'e-2 on Thursday set off from its moon orbit for outer space about 1.5 million km away from the earth, Chinese scientists said Thursday.

The orbiter left its moon orbit at 5:10 p.m. and it will take about 85 days for the orbiter to reach outer space, according to the State Administration of Science,Technology and Industry for National Defence (SASTIND).

The orbiter had finished all its tasks within its designed life span of six months by April 1.

Scientists decided to let it carry out additional exploratory tasks as the orbiter still had fuel in reserve.

Traveling into outer space from the moon's orbit is the most important task among five additional ones, according to the SASTIND.

"It's the first time in the world for a satellite to be set off from the moon in remote outer space," said Zhou Jianliang, deputy chief engineer of the Chang'e-2 measure and control system of the Beijing Aerospace Control Center (BACC).

Before flying away, the orbiter had finished two additional tasks as of May 23.

One was to take photos of the northern and southern poles of the moon. The other was to descend again to the perilune orbit, about 15 km away from the surface, to catch high-resolution images of the Sinus Iridum, or Bay of Rainbows, the proposed landing ground for future moon missions.

Scientists hope the satellite can continue operations until the end of next year.

Nine kilometer-wide Laplace A (43.64° N, 333.33°E) is a familiar nearside feature because of its place in the largely "featureless" landscape along the frontier of the northwest Mare Imbrium and Sinus Iridum. The crater, also extensively surveyed by NASA's LRO - see links below - has "pre-excavated" Imbrium seabed over the inundated "missing" southeastern outer ring of the Iridum impact. A rewarding 7000 pixel-wide, very detailed version of the image is available from tantaonews.com [CNSA/CLEP].

"We are developing outer space measure and control stations in outer space and they will be capable to carry out tasks by the end of the second half next year," said an SASTIND scientist, who declined to be named.

At that time, the satellite can be used to test the two stations' functions, the scientist said.

Challenges exist as Chang'e-2 was not designed for the additional task and it is now in extended service without extra capacities to deal with abnormal risks, Zhou said.

Meanwhile, long-distance brings many problems like weakening signals and difficulties in measure and control, Zhou said.

The Chang'e probes are named after a legendary Chinese moon goddess who flew to the moon.

Besides the current operations, China's ambitious three-stage moon mission will include a moon landing and launch of a moon rover around 2012 in the second phase. In the third phase, another rover will land on the moon and return to earth with lunar soil and stone samples for scientific research around 2017.

The country has no plan or timetable for a manned moon landing for now.

China launched its first lunar probe, Chang'e-1, in October 2007.

It became the third country after Russia and the United States to send a person into space in 2003. Two more manned space missions followed with the more recent in 2008 involving the country's first human space walk.

Like snowballs rolling down a ski slope, these boulders create clear impressions in the lunar regolith before coming to rest at the base of the slope (the floor of a closed depression in Oceanus Procellarum near Aristarchus crater).

We see them lining up where the slope angle changes. If they had been rolling quickly, we would expect that some of them would be carried beyond this point by their momentum. The fact that most of them line up nicely at the break in slope therefore tells us that they moved slowly in the low-gravity lunar environment, perhaps taking a long time indeed to complete their journeys down the slope, and that simply arriving at the floor was enough to prevent further travel.

Context image from NAC frame showing perimeter of rille floor and greater area of boulder coverage; image is ~1.3 km across [NASA/GSFC/Arizona State University].

The larger NAC context image shows similar downslope boulder rolls have occurred around much of the depression perimeter. The full NAC image shows the surrounding mare beyond the depression, and also helps to illustrate the origin of the depression floor: it seems to be the result of flow into the depression from mare material outside the depression. A breach in the wall can be seen at the north end of the feature, with mare material flowing downslope and partly filling the valley below. Is this telling us something about the timing of the depression formation relative to mare formation? What other clues would you look for to prove your hypothesis? What kind of depression is this ... a short rille, volcanic caldera, or something else?

A portion of the global WAC mosaic showing the Featured Image central depression and surrounding mare of Oceanus Procellarum; image is ~57 km wide; north is up; bright ejecta rays are from Aristarchus crater to the northeast [NASA/GSFC/Arizona State University].

This rubble represents a portion of fall-back debris deposited shortly after crater formation, mixed with subsequent landslide debris, and partially covers the floor of a small, fresh crater located near Rocca crater in the Lunar Highlands. If you scan the expanded thumbnail image carefully, you may see what appears to be small deposits of impact melt nestled among the larger blocks and sediments ... or are these fine debris flow deposits? What clues would you look for to make the distinction?

If this loose rubble were to become buried, compacted, and lithified, we would call the resulting rock an impact breccia. Impact breccias are one of the features that geologists look for who study terrestrial impact sites, where often times all the other obvious crater features have been filled in and/or eroded away. Since there is no wind or water to erode or bury these deposits on the Moon, such features are perfectly preserved -- as if they had formed yesterday just after breakfast!

Near-full-width NAC frame M112047758R showing full crater morphology; field of view is approximately 1.9 km[NASA/GSFC/Arizona State University].

Explore the full NAC image HERE. Notice that the rubble pile is located off-center from the crater floor. Perhaps this was caused by a low-angle impact that resulted in an asymmetric debris cloud. Note also the dry debris flows cascading down the sloping crater walls. Does this finding effect your interpretation of the fine materials on the crater floor that look like impact melt?

Neil Armstrong and Buzz Aldrin, back in lunar orbit flying the ascent stage of the Apollo 11 lunar module, approach Michael Collins in the command module for their return to Earth, following the first manned expedition to the lunar surface in July 1969 [NASA/ASJ].

Features such as this "dark-haloed" crater are not common on the Moon, but where found there tend to be occurrences of both mature volcanic deposits, and fresher (more recent) impact ejecta deposits. This circumstance provides clues for solving the light/dark mystery in a straightforward manner. For example, this crater is located to the north of Liebig J, a relatively young, bright-rayed crater in Mare Humorum.

The Featured Image impact clearly occurred within the Liebig J ejecta blanket, which is less mature and therefore of higher albedo than the surrounding dark mare rock. When the small impact took place, it penetrated the Liebig J ejecta and excavated the darker material from beneath.

Note that some of the material within the crater wall is actually brighter than surrounding material. This is not too unusual with fresh craters. But why was the dark ejecta not distributed in a perfectly even and symmetrical way? It would probably require the collection of samples and field mapping on the ground to answer this completely. But part of the story may be due to textural heterogeneity (clumpiness) of the Liebig J ejecta deposit in this area. When the dark-halo impact occurred, such clumpiness may have caused the impact energy to disperse in an uneven way. Note also that more recent, smaller craters have punctured through the dark ray pattern to re-expose the brighter deposits beneath. The end result is a complex local stratigraphy, but one which can be unraveled through a careful study of the effects of impacts, their energies, and locations. The context image below shows the albedo difference between the Liebig J ejecta deposits and the surrounding mare deposits.

A portion of the global WAC mosaic showing the Liebig J crater region of western Mare Humorum and its bright ejecta [NASA/GSFC/Arizona State University].

Explore the full NAC image HERE; notice the ejecta of the prominent Liebig J crater. How many similar dark-haloed features can you find?

Friday, June 3, 2011

A granular debris flow on the wall of Stevinus A (downhill to the bottom, to the right in the original full-size LROC Featured Image). A 7 meter boulder impedes the progress of the flow, which bifurcates and reconnects about 10 meters further downhill. LROC Narrow Angle Camera (NAC) observation M154893929R, LRO orbit 7960, March 16, 2011; image field of view is 200 meters wide [NASA/GSFC/Arizona State University].

Lillian OstrachLROC News System

Stevinus A (31.75°S, 51.55°E) is an 8 km diameter crater with very smooth, high albedo crater walls and low albedo streamers and streaks. The high albedo material composing the crater walls may have once been an impact melt veneer that is eroding over time as micrometeorite bombardment promotes regolith formation. Sometimes, craters with smooth walls are observed because the craters are old enough (at least Eratosthenian age, where their ejecta rays have been erased) to have developed a regolith layer that blankets the interior of the crater and obscures small-scale morphology variations. However, Stevinus A is pretty young and has only recently begun to accumulate a thin regolith because there are distinct edges observed (above the boulder mentioned in the opening image, for example) as well as boulder trails (also observed in the opening image).

Stevinus A crater is home to many unique features, but the low albedo flows on the crater walls are striking. Are they impact melt flows that splashed onto the crater walls and flowed downhill, toward the crater floor? Or are these flows composed of granular, dry debris that acted like a fluid when the particles were mobilized, perhaps by a seismic shock wave from a nearby impact? Moreover, why are these streamers composed of such low reflectance material when the rest of the crater is of higher albedo?

LROC Wide Angle Camera monochrome mosaic of Stevinus A and vicinity. Location of LROC Featured Image, June 2, 2011, noted with asterisk [NASA/GSFC/Arizona State University].

In the opening image and elsewhere in the LROC NAC image pair, there appear to be two kinds of low albedo material. One type is rubbley and contains discernible rocks, scattered across sections of the crater wall. The other type looks smoother and occurs in braided stream-like flows and cuts through the more rubbley material. Although at first glance these braided streamers seem to be impact melt flows, closer observation suggests that they are probably the result of dry debris flows of fine-grained material. Granular flows are not uncommon on the Moon, especially on steep slopes like crater walls, where the slope is greater than ~20° and not quite the angle of repose, which is ~30°. Dry granular flows are also observed on Mars and even on the asteroid Eros! Furthermore, the braided nature of these flows suggests successive depositional periods. If these streamers are dry material, successive depositional events may be triggered by disturbance from a boulder bouncing downhill, and in the opening image there is evidence of at least one bouncing boulder.

These observations are consistent with a dry, granular debris flow from the higher elevations on the Stevinus A crater wall toward the crater floor. However, there is impact melt in the crater floor, along with bouldery and blocky ejecta debris (and probably debris flows, too!) observed in another LROC NAC pair of Stevinus A. Thus, to help make a definitive interpretation of these low albedo streamers traveling down the crater walls, a stereo pair of the crater would allow LROC scientists to measure the slope of the crater walls.

Can you find evidence in the full LROC NAC image for disruption of the flows by boulders? What about other downslope movement; do you observe any higher albedo material traveling down to the crater floor?

Thursday, June 2, 2011

Spectacular rubbley impact melt, flowing away from its parent crater. Across the widest part of the terminal lobe, the flow is ~115 meters. LROC Narrow Angle Camera (NAC) observation M153863408R, LRO orbit 7809, March 4, 2011; image field of view is 500 meters. See the full-size LROC Featured Image HERE [NASA/GSFC/Arizona State University].

Lillian OstrachLROC News System

Yesterday's Featured Image highlighted boulders eroding out of a hill in the Anaxagoras crater impact melt pond. The opening image above highlights an impact melt flow located on the lunar far side at 23.99°N, 209.94°E.

The impact melt flowed from its source crater through rubbley ejecta before it cooled. There are several lobes at the terminus of the flow; perhaps these lobes "broke out" when the surface of the flow cooled but the interior of the flow remained hot and could still flow. The farthest-reaching lobe extends for about 95 m past the large lobe. There are some small boulders, around 10 meters across, that are entrained in the impact melt, but most of blocks close by seem pushed or maneuvered there by the flow, much like a levee formed during a volcanic flow.

LROC Wide Angle Camera (WAC) monochrome mosaic context view of the impact melt flow. Asterisk notes the flow, which is located in a relatively typical far side highland area (lots of large, old craters, few large fresh craters, and no mare) See the full-size WAC context image HERE [NASA/GSFC/Arizona State University].